Draft damper



June 15, 1937. HITCHCOCK I 2,083,844

DRAFT DAMPER Inventor For vest L.Hit.chcocra I mnega June 15, 1937. F. L.,H|TcHcocK 2,033,844

DRAFT DAMPER Filed May 14, 1934 2 Sheets-Sheet 2 Inv enter f 4- v by Fovveat LHltchcoch I *3 m um Atwmega Patented June 15, 1937 UNITED STATES A PATENT OFFICE 1mm DAMPER Forrest L. Hitchcock, Indianapolis, Ind., assignor to Furnaslave, Inc.

Application May 14, 1934, Serial No. 725,558

1 Claim. (01. 236-96)- bodying the invention is so designed that when the draft is cut off from the furnace, the heat within the chimney willbe preserved so that the chimney or stack will not be cold when the draft is to be resumed through the furnace. A further primary object of the'invention is to prevent the drawing out of warm air from the furnace room when the draft through the furnace is inter rupted by the damper so that the operation of the damper will not induce' a flow of cold air into the building or. room wherein the furnace is placed.

Other advantages and objects ofthe invention such as the control of the damper through a very simple operatingv mechanismand cheapness of construction, will' become apparent to those Fig. 5, a. detail in vertical section on the line- 5-5 of- Fig. 3;

Like characters of reference indicate like parts throughout the several .ews in the drawings.

The invention is' particularly adapted to be employed in connection with some sort of an automatic burner or stoker herein generally .des ignated by the numeral I 0,Fig. 1, which is here shown as being connected with a warm air furnace having a smoke pipe l2 leading to a chimney or stack l3. The smoke pipe I2 is provided with an opening, here shown as being on its upper side, about which opening is placed a housing l4 having its upper edges terminating in a common horizontal plane with a finish strip I5 therearound, here shown as in the form of an angle iron.

A shaft IB is rockably carried transversely across the housing I5 near the upper side thereof and toward the end adjacent the furnace. Fixed to theshaft i6 is a plate ll formed to fit freely within the housing so that it may swing downwardly to extend across the pipe l2 therewithin in some such position as indicated in Fig. 4. The length of the plate I1 is made to be such that when in the downwardly hanging position, a

passage will be left thereunder so. as to permit gases to escape fromthe furnace through the pipe l2 and into the stack l3 although the major movement of gases and air therethrough is retarded by the presence ofthe plate IT. This plate I1 is further formed to be of that shape and proportion to have the plate ll fit closely againstthe under side of the inturned leg of the angle iron if: when the shaft Isis rocked to swing the plate ll upwardly thereagainst.

A crank I8 is fixed to one end of the shaft IS on the outer side'of the housing [4 as a means of rocking the shaft IS. A rigid connecting link is is pivotally secured to the outer end of the crank l8 and hangs downwardly to be pivotally connected to an end of a bar 20. The other end of this bar 20 is securely anchored to a fitting 2| which is secured in place along the side of the pipe l2. This bar 29 is a bimetallic member so that when heat is applied thereto it will bein relation to the swinging travel of the crank |8 so that the. desired degree of travel of the plate: may be produced. The bar 2|! carries an electrical heating element 22 therearound of a suitable resistance so as to set up a heating effect on the barZiJ when current-flows through the element. The fitting 2| is adjusted initially to the position indicated in Figs. 3 and 4 to have the bar 20 elastically pulling downwardly on the link I9 so as to rock the plate I! to its closed or lowermost position. This positionis determined by the adjustable screw 23 which extends through the angle iron l5 to have its end abut the plate H from the under side thereof.

When an electrical current is sent through the element 22, sufficient heat is generated therein to cause the bar 20 to warp or bend upwardly (the bar 20 being so turned as tohave its motion in that direction) as indicated in Fig. 4 by the dash lines, so that the link l9 will be pushed upwardly to rock the crank l8 and in turn rock the shaft ll so as to lift the plate ll to its upper position against the under side of the overturned leg of the angle iron Hi. In this position the normal draft through the pipe I! may be hadwithout interference of any damper members. Now when the heat produced by the furnace II is sufficient, the electrical current flowing through the element 22 is interrupted by any suitable means (not here shown), which means does not form a part of this particular invention. In this regard reference is had to my Patent No. 2,041,833, issued May 26, 1936 as relating to a control system. Upon the interruption of this flow ofcurrent, the bimetallic member 20 will then start to cool and returnto its normal straight position so as to rock the plate I1 around to the reduced draft position again.

When the plate I! is in this reduced draft position, air may enter through the open upper end of the housing II and flow into the pipe l2 and on into the stack l3. This fiow of air, however, may be objectionable in that it would ordinarily tend to pull warm air out of the room and even adjoining rooms wherein the furnace is located which would cause a reduction in temperature and loss of .heat therein. Not only would such a condition arise but also the air entering through the top of the housing I would have a tendency to reduce the interior temperature of the stack B so that when the plate I! was again rocked to the full draft position, the draft would not then be of that intensity which prevailed just prior to the shifting of the plate I! to the closed draft position since the reduction of temperature in the stack l3 would tend to reduce the movement of air therethrough. It is desirable to maintain the draft through the stack I3 at the.

same rate of flow so as to give a better regulation of fire control in the furnace ll.

Therefore I preferably include in my damper construction an auxiliary plate 24 which is also secured to the shaft IE to be rocked therewith. The plate 24 is shaped to fit down snugly over the top side of the angle iron l5 and is so positioned on the shaft l6 that it will be in contact with that angle iron 15 when the plate I! is rocked to the no-draft position. In this way the flow of air into the housing I4 is completely cut off when the draft through the pipe H from the furnace II is at the minimum flow thereby conserving heat not only within the room but also within the stack l3. Preferably a counter-balance weight 25 is employed to balance the weight of the plates I1 and 2 so that the bar 20 will not have to carry the weight thereof.

'The bimetallic. bar. 20 is elastic and thereby providesa yielding and cushioning member in the operating system which is particularly effectivewhen the plates H and 24 reach their closing positions. When the plate I! is shifted to its for such controls.

upper position so as to give full draft through i the pipe l2, the elasticity of the bar 20 permits the plate I! to drop downwardly slightly under suddent reductions in pressure thereunder as may be induced'in the pipe I! by gusts of wind across the top of the stack I3. This action helps to maintain a constant draft through the furnace ll'practically unaffected by these gusts of wind and also by variations in draft set up by differences in out-of-door temperatures and also by tall stacks giving more than a predetermined required maximum draft.

In order to protect the element 22 about the bar 20, I preferably employ a housing 26 thereover in spaced relation. By use of the bimetallic bar 20 with the heating element 22 therearound, I am able to effect a shifting action of the damper members without having to employ motors or solenoids heretofore considered to be necessary By use of my structure, a silent and effective operation is secured with perfect reliability. I

It is to be noted that by employment of the combination of plates l1 and 24, the closure of one does not set up a draft resistance to the opening of the other. Also, the plate I! closes elastically against the gas flow from the furnace, permitting those gases to lift the plate I! to escape in case of a hot fire. The area of the opening through the pipe and housing is such that draft increases on the forward or stack side of the plate I! do not affect the draft therebehind as determined by the position of the plate [1.

While I have herein shown and described my invention in the one best form as now known to me. it is obvious that structural changes may be made without departing from the spirit of the invention and I therefore do not desire to be limited to that precise form beyond the limitations as may be imposed by the following claim.

I claim:

The combination with a smoke-pipe leading from a furnace to a stack, said pipe having an air inlet, a rock shaft mounted transversely across the inlet, a damper plate fixed to the shaft to swing down into the smoke pipc, an auxiliary damper plate fixed to the shaft at an angle to the first damperplate to swing to close said inlet as said first damper plate swings into the smoke pipe, a set screwadjustable toward and from the first damper plate to determine the maximum movement of said plate into the smoke pipe, a. crank fixed to the rock shaft, a bimetallic bar, formed of a plurality of strips having different coefficients of expansion pivotally attached to the crank, a fitting to which the other end of the bar is attached and means for rotatably adJusting the fitting to adjust the position of the bar in relation to the position of the crank.

FORREST L. HITCHCOCK. 

